A convenient method of warehousing goods is to stack goods on pallets and insert the loaded pallets into storage bays using fork lift trucks or the like. A common warehouse arrangement has a pair of back-to-back arrays with each array facing an aisle. Each array includes a plurality of storage bays in horizontal and vertical rows. It is recognized that a warehousing arrangement which requires one aisle for two arrays, each one load deep, is wasteful of floor space, and storage racks have been proposed having greater depth whereby loads may be stored at more than one location within each bay.
U.S. Pat. No. 4,155,462 discloses storage racks for receiving two loads of palleted goods through a front end, thereby essentially doubling the amount of storage area associated with each aisle. A first load of goods is placed upon a trolley in the storage bay, and the loaded trolley is moved rearward along a track to an inner location when a second load is inserted in the same bay. The trolley, which is biased forward by resilient means, returns its load to the front location of the bay when the second load is removed.
In the system described in U.S. Pat. No. 4,155,462, the weight of the second load prevents the forward return movement of the trolley until it is removed. It is recognized in the '462 patent that a light load in front of the trolley may be insufficient to prevent forward movement of the trolley; however, as the system is intended for use in warehouses of large capacity, this danger is dismissed as minimal. While the danger of a forward-biased trolley pushing a fully loaded pallet into the aisle may be minimal, such may not be the case when a pallet is nearly empty. In many warehouse facilities, goods will frequently be individually picked from a loaded pallet rather than withdrawn as an entire pallet load. If the load becomes sufficiently light, a forward-biased trolley may dislodge the pallet and shove it and the remaining goods into the aisle.